FIG. 4.

Gel mobility shift assay of cadB regulatory DNA with purified SoxR. (A) Facing sets of 17-mers were used for PCR to obtain DNA probes a (from position −97 to +64), b (from −166 to −38), and c (from −10 to +119), which were then labeled with [γ-³²P]ATP. (B) Gel mobility shift assays were performed as described in Materials and Methods. Probe a was incubated with increasing concentrations of purified SoxR (0, 50, 100, 200, and 400 nM), whereas probes b and c were incubated with 400 nM purified SoxR protein. Free probes (FP) and binding complex (C) are indicated with arrows.